Unaccompanied foreign minors (UFMs) face stigmatisation and social exclusion in Spanish territory. Given their growing presence in schools, it is crucial that trainee teachers have valid and real information about these students in order to provide equitable, personalised, and quality education to all their students in the near future and to mitigate any uninformed prejudices and stigma developed before they enter the classroom. This study seeks to validate a scale designed to assess the perceptions of pre-service teachers about UFMs (n = 169). The objective of this study was to validate a scale designed to assess the perceptions of pre-service teachers about UFMs (n = 169). All participants were studying primary education at the University of Granada (Spain) [♂ = 131 (77.5%); ♀ = 37 (21.9%)]. Methodology: A quantitative, descriptive, cross-sectional, ex post facto, and quantitative study was conducted. The data were analyzed with IBM SPSS® 28.0 and IBM Amos Graphics® 23.0 programs. Results: A multidimensional scale was developed with a Cronbach’s alpha of 0.858 and McDonald’s omega of 0.859, consisting of a total of 26 indicators divided into three factors: socio-educational characteristic (n = 13), social threat (n = 7), and physical and emotional well-being (n = 6). The general scale showed high reliability and acceptable fit (p < 0.001; KMO = 0.880; GFI = 0.832; IFI = 0.925; NFI = 0.816; CFI = 0.924; SMSR = 0.058). CFA reports that the items with the highest factor loadings are related to determining whether these minors respect cultural differences, are involved in drug trafficking, and arrive in Spanish territory with significant malnutrition. However, the items with the lowest factor loadings are linked to understanding the type of academic education these minors have, whether they consume alcohol, or if they require teachers with intercultural competencies to help them integrate socially. Conclusions: A reliable and robust scale was developed to assess the perceptions of pre-service primary school teachers about unaccompanied foreign minors. This instrument can be used to identify the knowledge of teachers in training, which allows training actions to be implemented in the context of higher education to raise awareness, detect biases, and make this vulnerable group visible.
